In recent years, researches on resins synthesized from raw materials derived from plants without using petroleum have been extensively carried on in order to cope with environmental problems such as global warming and exhaustion of fossil resource. In particular, researches on polylactic acid as a resin derived from plants have been carried on, and various products have been introduced to practical applications.
Thermoplastic resins typified by polylactic acid are generally classified into non-crystalline resins and crystalline resins, and the latter resins can be crystallized by a heat treatment. In the case of the crystalline resin, its heat resistance can be improved by crystallization, so that the resin is desirably crystallized before use rather than used in a non-crystalline state. However, when the resin is subjected to, for example, injection molding, it is necessary to hold the resin in a temperature-controlled mold for a certain period of time after injecting the resin for sufficiently conducting crystallization, and it is necessary to increase the crystallization rate thereof for improving productivity.
In order to use a resin composition as an injection-molded product, the resin composition is often required to have high heat resistance for the reasons in terms of service and transport environments of the product. Therefore, the resin composition is required to combine high crystallization rate with high heat resistance for practical applications.
As a technique for increasing the crystallization rate, it is known to add a crystal nucleating agent into a resin composition. For example, Japanese Patent Application Laid-Open No. 2007-191630 has reported that a phosphoric ester metal salt is effective as a crystal nucleating agent for polylactic acid that is a typical plant-derived resin, and NA-11 (product of ADEKA Co., Ltd.) is particularly most suitable for the agent.
On the other hand, polyethylene furandicarboxylate is known as a plant-derived resin. The merit of polyethylene furandicarboxylate is to have excellent heat resistance compared with polylactic acid. However, the most suitable crystal nucleating agent for polyethylene furandicarboxylate has not been yet known.